Yeti 2.0 tdci elegance 4x4 - "Control system for exhaust" warning light

[burntcrisps2]

Recently had this warning light come on "Control system for exhaust" and stay on when setting off in car.

Checked the manual and it says...

 

The warning light  comes on after the ignition has been switched on.
If the warning light does not go out after starting the engine or it lights up when
driving, a fault exists in an exhaust relevant component. The engine management
system selects an emergency programme which enables you to drive to the nearest
specialist garage by adopting a gentle style of driving.

 

However the engine ran as normal and pulled fine, so not in a limp mode, just a warning light on.

Unable to check anything via diagnostics, but fault and description and internet searching led me to believe it would be one of the sensors in the exhaust system that had failed or possibly a bad connection.

 

Managed to get a local garage to take a look at codes the following day and they discovered the code was actually PO121 - Throttle valve faulty signal, which didn't make sense as that's petrol related, but turned out to be the accelerator pedal for diesel.

They removed and cleaned connections and replaced and the error disappeared.

 

It worked fine for about a week and then the light again came on and stayed on.

Turned the engine off and gave the accelerator pedal a good couple of rapid depresses, full travel.

 

Started again and light went off and been off since for several weeks, so looks like its cured, but may re-appear.

 

Anybody else had the same issue?

Did you eventually have to replace the accelerator pedal assy.?

 

[kenfowler3966]

Sounds like the car has had the "fix", and one of the components can't manage working harder than originally intended?

Back to the dealer and hope the fix warranty has some value?

[burntcrisps2]

Correct it has had the fix, forgot to mention it was done back in Nov2016 and has been working fine since then, although have noticed when parking fans running as still doing regen.

Will see what happens over coming months.

[kenfowler3966]

Thats the whole point. Fix makes some components work much harder and fail sometimes immediately or better for VW/Skoda some time later so they can argue it wasnt caused by the fix and you need to pay. Anyone thinking I have had the fix and all is fine is in that brief period of naively thinking they are helping the environment before problems may well occur.

 

Hence my wifes Fabia will never have this downgrade fix applied which actually is only a political excercise and from tests makes no difference to normal use nox emissions and may even increase co2 as more fuel is used to burn of esultant extra soot. Hence egr valves soot up and fail, dpfs block up sooner and more frequent regens waste fuel and producemore co2.

 

Whats worse in some cars the egr valve is easily accesible and can be cleaned or replaced at minimal cost or even a practical diy job. On Yeti it is so difficult to reach a dealer has to do it and it is never worth reusing the old one.

Edited 7 September, 2017 by kenfowler3966

[Ootohere]

Report Officially any concerns about Post Fix behaviour, 

VW Group were saying only 1% reporting issues when 1/2 a million or so of vehicles mostly owned by VW Finance or VW Group in the UK were done.

If there are issues then best have them on the Skoda Dealership / VW System for future reference.

After all they are going to be paying for premature failures.

[burntcrisps2]

Is there an official link to report any concerns post fix? Want to make sure it gets logged in the correct place.

 

The issue has occasionally happened in the months since originally posting and its never shown any limp mode or adverse driving.

Back in Nov 2016 I looked at the web to see if any issues with having the ea189 fix, but only found some minor ones reported at time with some VW models.

Since the fix was supposed to remove the defeat and nothing else, we decided to have the fix done.

Turns out that VW lied about the fix in that it did a lot more than remove the defeat.

I would not have had it done if we had known, but I see many garages have implimented even though customers have specifically said never do this and then the garage still will not reverse fix back to original.

[voxmagna]

I know the OP posted in September but others searching and finding this thread might be helped by my recent post:

 

The TV problem is probably not fixed and the accelerator replacement could have been unecessary?  The accelerator pedal assembly is a very robust electronic design without mechanical moving resistor parts. Hitting the accelerator pedal hard at idle just forces the throttle flap valve to move between extremes, suggesting it is already gummed up. We can't prove it, but they probably swapped out the accelerator pedal for no reason, then they did an emergency idle dpf regen. which apparently fixed the fault. BUT IT WILL COME BACK. This fault code is not one that puts on limp home. BUT it stops automatic regens from starting and the dpf will fill up with soot whilst the fault lamp is lit!

 

They should have removed the throttle valve assembly and inlet manifold for inspection and clean. At the very minimum they could have inspected the TV in situ with a snake camera (15 minutes work). If it was significantly clogged like mine after 50k, suspicions should then move on to the condition of the EGR cooler assembly and the dpf. Both the latter are difficult to get to and expensive but making sure they are clean should offset future problems for some (unknown) mileage.

 

 

[burntcrisps2]

Interesting info posted by voxmagna, however no parts have been replaced on this vehicle and sometimes the fault disappears on its own with no user interaction.

The symptoms do gel with it being a poor intermittent connection and on the odd occasion the fault has been cleared by simply removing the throttle valve connector or the accelerator connector and then reconnecting.

The car drives normally and always has before and after the VW emissions fix.

It has the same apparent power, acceleration and fuel consumption before and after.

The DPF regens more frequently than before, but has not shown any failure to not do so.

I purchased an android phone and the VAG DPF app just to monitor and it shows its working and the DPF is normal.

The symptoms do look like electronic issues, (I am an electronics engineer by training, customer services manager), so well aware that everything in life fails, whether it is man-made or in nature and electrical connections are the weak point of any electrical/electronics setup. However it is still just as likely to be the effects of the ea189 VW fix, as a whole year has gone by and the issue has only recently come to the surface.

I hadn’t seen your post that you have linked to, but will investigate the throttle valve and see how gunked up it is and clean as I am sure it will need it like any diesel engine, no matter what mileage. Great post by the way. Thanks.

Interesting to note you had a different fault code P0120 (mine is P0121) and whilst fault codes are useful, they can also be misleading.

One other point regarding the reply thinking this might be a sticking throttle valve.

I stated… Turned the engine off and gave the accelerator pedal a good couple of rapid depresses, full travel. This would not have done any movement of the throttle valve as it was turned off. If anything this was rattling the connections and maybe related to a bad connection. Accelerator pedals do fail and so do throttle valves.

It is random/intermittent, but appreciate this could easily be gunked up components too. Will investigate soon.

I have also been looking at cgon ezero1 product and spoken with cgon about fitting this device to the Yeti. They will do a case study to see the effect as they have not done a fixed ea189 when last spoken with them.

Roll on the day we swap one of our cars for an EV and give up with diesel over the next few years.

 

[burntcrisps2]

Well I managed to find time to look at the throttle valve assy. last Saturday 30Dec2017 as weather was semi OK to do this outdoors.

First I looked at the official elsawin documentation on how to replace. Removing and installing the throttle valve control unit -J338-pdf. I have attached the pdf should anyone need it (along with the Intake manifold - remove and install pdf)

That details removing the inlet pipe assy (Charge air hose – plastic pipe with sensor and a rubber pipe coupling at either end) that routes from the front left of engine bay across and up the front of the engine.

Looks simple but the pictures don’t show the fact that there is no room to get your hand in to undo 2 bolts.

I looked at the top rubber coupling and decided it had 2 jubilee clips and was curved so should be easy enough to get just that rubber pipe off.

Not quite that easy as the top jubilee clip would not rotate.

I got it off anyway and discovered the top jubilee clip had 3 barbed clips that were actually stapled into the very top of the pipe.

I totally removed the 3 barb clips as they were just clipped over the jubilee clip so it would be easier to re-assemble and take off again in the future, should I need to.

I also looked at removing the air intake pre filter pipework as that looks like it should give some more room for hands and tools. I managed without removing, but should be easy enough to take the U shaped piece off. Think you need to remove the filter to access clip(s) inside to pull it out.

 

I have removed diesel inlet air manifolds from other cars and cleaned. But it is almost impossible to do fully unless you have some industrial cleaning equipment. Maybe a large ultrasonic bath, or something you fill with large amounts of cleaning fluid. You will need bottle brushes, old toothbrushes etc. and once done it won’t be 100% clean, as you usually can’t get to all the internal surfaces, so unless it’s obviously almost blocked on the in and out ports it’s in my opinion not worth the hassle. If it’s not broken, don’t fix it applies here. If the issue is just the throttle valve, just fix that.

 

I strongly suggest using plastic tools to scrape off the heavy deposits, something like old credit cards cut into strips works well, just file off any sharp corners and edges before using. Along with old nylon toothbrushes and plenty of rags and cleaning fluid. (I had a can of Wynn’s diesel egr3 cleaner already, so used that along with petrol.)  Using any metal tools will more than likely scratch/score the assembly so best not as it’s a precision device.

 

So my decision was just to remove the throttle valve and clean and replace.

I also looked at the exhaust gas recirculation pipe and the info saying to turn the nozzle part through 180 degrees. I hadn’t understood the dialogue about this till disassembly. Quite simply it sprays exhaust gunk straight onto the throttle valve and if the valve is closed it is so close it peppers it with gunk as the thimble style inlet into the airflow is pointing straight at it. Turning it though 180 degrees means it flows into the air inlet manifold in the direction of the cylinders. I suspect some design engineers decided the original setup was best for egr and air mixing and I might agree if the valve was some 6” or 15cms away. There was talk of this being an Audi mod. Not sure if this is an official mod or even VAG mod, but regardless if you have one of these EA189 engines it’s a simple must do at any mileage to help stop issues with the throttle valve assy. Worth doing at any service at any mileage. Wish the Skoda garage had done this on any of its 5 yearly services with them from new.

 

I have attached some before and after pictures and some are taken with a mirror below the throttle valve so it was easier to take pictures with item in place before and after removal.

You can see the build-up of gunk on the left side of the butterfly valve which is where the exhaust gas shoots onto it. The shape of the gunk is tapered to the right and shows the build-up is worst at the far end of the assembly, the non geared side, meaning any sticking at this end is hard work for the motor and gearing. If you look behing the butterfly you can see the thimble style exhaust gas input with a rectangular cut-out. Later picture shows it cleaned and rotated through 180 degrees.

 

I am expecting to wait many months before I can say if this has cured the intermittent issue we have seen of the random P0121 error mesg. I am not the primary driver of this vehicle.

I will post an update in the future with results.

 

It is entirely possible that this clean up fixes it, but also that the fault is really an intermittent connection issue. Only time will tell.

 

Having written this up, I have had the pleasure of driving the vehicle for a number of mixed local and motorway travels. I have previously looked at getting a cgon ezero product and wanted to know what the DPF is doing, so I purchased an android phone just so I could use the VAG DPF app. I have been using this app as a data logger. It works fine and collects some good data. However as I said I am not the primary driver and it needs to be launched each time the car is started. So the data has some holes, but it shows a nice pattern. I have yet to find a way for it to auto reconnect once the car is locked as it needs the ignition on for the solution to work. I need to follow up with the developer to see if there is a way round the reconnect issue.

 

Anyway, over the last few months it has shown the DPF regens are happening at about 200 mile intervals. Which is reasonable for any ea189 engine with the VAG fix xxxxx, but I understand the fix has basically halved the interval for regens, so I presume it used to be of the order of every 400 miles.

 

I was staggered to discover that the latest set of data I pulled of the VAG DPF app showed the last regen interval was some 375 miles!!!

I can’t explain how the cleaning of the throttle valve assy and the rotating of the exhaust gas nozzle has made such a difference. Yes it’s cleaner and very slightly less restricted. The last tank fill to fill also seems to show a slight mpg improvement. Again I wasn’t expecting that. I will continue to monitor and post any updates. The car is not doing a high mileage, maybe 6 to 8K a year and its now 6 years old and only done 50K.

Attached some data graphs to show the regen below...

 

The engine/car is as below…

Sales model       5L734Y

Engine code       CFHC

Gearbox code   NFR

4x4 Haldex         4^th Generation

 

 

Throttle valve - remove and install.pdf

Intake manifold - remove and install.pdf

[voxmagna]

I didn't find a problem cleaning the plastic manifold? The carbon deposits are soft, I used a nylon bottle brush, brass boiler cleaning brushes and kerosene. I've tried the Android app. It requires a compatible and genuine OBD device and is not compatible with all engines. The reason is V.W use their own proprietary PID codes for exhaust diagnostics. Standard OBDII readers don't see the codes and only Torque pro (paid for) and vag dpf app. authors have discovered the codes for vag engines they know about. I have an older 2007 vag car that can only be read by Ross-Tech vcds at the moment.

 

Because of the need to have an Android device with engine compatible software and a more expensive ELM Bluetooth OBD tethered to the car (of which I have 2) I have decided to design a simple dpf regen. monitor which can be hard wired and should work with most vag vehicles. It will count the number of regen. cycles from a mileage starting point whilst indicating dpf temperatures in real time. No fancy bar graph charts, but it will be running when the ignition is turned on and give a short non-intrusive short audible 'bleep' alert when the dpf is regenerating. 

 

Until somebody starts with a known clean throttle valve assembly (and EGR cooler assembly) after the E189 fix, we can't be certain the fix is evidence of a contributory cause of failure.

 

As I have researched and am designing my dpf regen. monitor, I have become aware of the possible temperature limitation on the VAG exhaust gas sensors. I expected the sensors to be 'K' type thermocouples with a maximum temperature of 1300 deg. C. They are not and that worries me if their fix has raised the dpf regen. temperature, because some here have said they have had theirs replaced? I think their current sensor design has a maximum working temperature limit of around 850 deg.C and more frequent (higher) temperature cycles could cause them to fail sooner. They can replace a failed exhaust gas sensor with new using the same design, but that won't guarantee the same long life if regen. parameters have now changed.

 

PS: You did what I did first and faffed about releasing the short hose, yes it's a real pain and only my magnetic catch allowed me to release and remove those bolts on the steel connecting pipe without dropping them. Which is why I would now disconnect clutter from across the top of the manifold and remove it with the TV attached.

.

Edited 6 January, 2018 by voxmagna

[burntcrisps2]

Sounds like voxmagna has discovered some other interesting facts regarding the exhaust gas sensors. I hadnt noticed anything that says the actual regen temperature has been raised on the fix, but if thats the case then yes the more frequent regens and higher temps will cause the sensors to fail sooner than expected.

 

Agree with faffing about, half the time spent doing a job like this is discovering which tools you have that are short, medium or long reach to be able to get to nuts, bolts etc. and get your hands in a position to effect undoing!

 

Trust you succeed with the regen monitor, sounds like a good idea. Have fun.

The ELM device I got was a wifi one, as I read some negative issues regarding bluetooth ones, cant remember what is was now.

The CFHC engine is supported so the app works fine, but I might try a bluetooth ELM device as it may reconnect more readily after many hours of timeouts.

 

I have also added this throttle valve and exhaust gas feed cleaning to the yearly maintenance schedule on the Yeti, as I think based on what I have seen already it is worth doing yearly.

 

I have also been in contact again with cgon and they have been awaiting some expensive kit to be delivered (PEMS and hub-dyno setup) so they can do a case study of a VAG EA189 fixed engine - 23R6.

So I am interested to go down this route asap.

It is said that the install of this acts a bit like a water softener and once fitted the years of "scale and scum" are disolved and removed.

As a many decades user of water softners I can vouch for them as a must have in hard water areas, which is most of the UK.

 

[voxmagna]

I've also had a water softener for years. Bet you haven't rejuvenated the resin bed after several years use and contamination? I don't throw it away and replace now. Next year I think I'll just disconnect the exhaust gas return pipe, pull out the 'diverter' insert on the T.V and put my snake cam in for a look. With the ignition 'on' the T.V flap should be open, I've not been around the EGR cooler rear end at the back, which is so hard to see. Do you know where the hole with the pipe flange going into the cyl. head comes out? That also seems a good candidate for a snake cam look see.

[muddyboots]

On 06/01/2018 at 22:11, voxmagna said:

As I have researched and am designing my dpf regen. monitor, I have become aware of the possible temperature limitation on the VAG exhaust gas sensors. I expected the sensors to be 'K' type thermocouples with a maximum temperature of 1300 deg. C. They are not and that worries me if their fix has raised the dpf regen. temperature, because some here have said they have had theirs replaced? I think their current sensor design has a maximum working temperature limit of around 850 deg.C and more frequent (higher) temperature cycles could cause them to fail sooner.

Don't know if it's of any use, but while I've been logging EGTs on mine, the highest I've ever seen is low 700s ºC on inlet to the DPF; this is on a Stage 1 mapped 170 running full throttle up a long hill, so should be worst case, and it's within the 850ºC range you suggest . During regens it's usually around 500-600ºC. Having said that, I have had one replaced......!

I'd be surprised if the actual regen temperature has been raised by the emissions fix - more likely the frequency has increased due to faster soot loading I'd have thought. Presumably the DPF and it's surrounding heat shielding etc is designed with a certain range of temperatures in mind, and if they just go and raise the temps....could be a safety issue?

[muddyboots]

On 06/01/2018 at 18:02, burntcrisps2 said:

Well I managed to find time to look at the throttle valve assy. last Saturday 30Dec2017 as weather was semi OK to do this outdoors.

First I looked at the official elsawin documentation on how to replace. Removing and installing the throttle valve control unit -J338-pdf. I have attached the pdf should anyone need it (along with the Intake manifold - remove and install pdf)

 

That details removing the inlet pipe assy (Charge air hose – plastic pipe with sensor and a rubber pipe coupling at either end) that routes from the front left of engine bay across and up the front of the engine.

Looks simple but the pictures don’t show the fact that there is no room to get your hand in to undo 2 bolts.

I looked at the top rubber coupling and decided it had 2 jubilee clips and was curved so should be easy enough to get just that rubber pipe off.

Not quite that easy as the top jubilee clip would not rotate.

I got it off anyway and discovered the top jubilee clip had 3 barbed clips that were actually stapled into the very top of the pipe.

I totally removed the 3 barb clips as they were just clipped over the jubilee clip so it would be easier to re-assemble and take off again in the future, should I need to.

I also looked at removing the air intake pre filter pipework as that looks like it should give some more room for hands and tools. I managed without removing, but should be easy enough to take the U shaped piece off. Think you need to remove the filter to access clip(s) inside to pull it out.

 

 

I have removed diesel inlet air manifolds from other cars and cleaned. But it is almost impossible to do fully unless you have some industrial cleaning equipment. Maybe a large ultrasonic bath, or something you fill with large amounts of cleaning fluid. You will need bottle brushes, old toothbrushes etc. and once done it won’t be 100% clean, as you usually can’t get to all the internal surfaces, so unless it’s obviously almost blocked on the in and out ports it’s in my opinion not worth the hassle. If it’s not broken, don’t fix it applies here. If the issue is just the throttle valve, just fix that.

 

 

I strongly suggest using plastic tools to scrape off the heavy deposits, something like old credit cards cut into strips works well, just file off any sharp corners and edges before using. Along with old nylon toothbrushes and plenty of rags and cleaning fluid. (I had a can of Wynn’s diesel egr3 cleaner already, so used that along with petrol.)  Using any metal tools will more than likely scratch/score the assembly so best not as it’s a precision device.

 

 

So my decision was just to remove the throttle valve and clean and replace.

I also looked at the exhaust gas recirculation pipe and the info saying to turn the nozzle part through 180 degrees. I hadn’t understood the dialogue about this till disassembly. Quite simply it sprays exhaust gunk straight onto the throttle valve and if the valve is closed it is so close it peppers it with gunk as the thimble style inlet into the airflow is pointing straight at it. Turning it though 180 degrees means it flows into the air inlet manifold in the direction of the cylinders. I suspect some design engineers decided the original setup was best for egr and air mixing and I might agree if the valve was some 6” or 15cms away. There was talk of this being an Audi mod. Not sure if this is an official mod or even VAG mod, but regardless if you have one of these EA189 engines it’s a simple must do at any mileage to help stop issues with the throttle valve assy. Worth doing at any service at any mileage. Wish the Skoda garage had done this on any of its 5 yearly services with them from new.

 

 

I have attached some before and after pictures and some are taken with a mirror below the throttle valve so it was easier to take pictures with item in place before and after removal.

You can see the build-up of gunk on the left side of the butterfly valve which is where the exhaust gas shoots onto it. The shape of the gunk is tapered to the right and shows the build-up is worst at the far end of the assembly, the non geared side, meaning any sticking at this end is hard work for the motor and gearing. If you look behing the butterfly you can see the thimble style exhaust gas input with a rectangular cut-out. Later picture shows it cleaned and rotated through 180 degrees.

 

 

I am expecting to wait many months before I can say if this has cured the intermittent issue we have seen of the random P0121 error mesg. I am not the primary driver of this vehicle.

 

I will post an update in the future with results.

 

 

It is entirely possible that this clean up fixes it, but also that the fault is really an intermittent connection issue. Only time will tell.

 

 

Having written this up, I have had the pleasure of driving the vehicle for a number of mixed local and motorway travels. I have previously looked at getting a cgon ezero product and wanted to know what the DPF is doing, so I purchased an android phone just so I could use the VAG DPF app. I have been using this app as a data logger. It works fine and collects some good data. However as I said I am not the primary driver and it needs to be launched each time the car is started. So the data has some holes, but it shows a nice pattern. I have yet to find a way for it to auto reconnect once the car is locked as it needs the ignition on for the solution to work. I need to follow up with the developer to see if there is a way round the reconnect issue.

 

 

 

Anyway, over the last few months it has shown the DPF regens are happening at about 200 mile intervals. Which is reasonable for any ea189 engine with the VAG fix xxxxx, but I understand the fix has basically halved the interval for regens, so I presume it used to be of the order of every 400 miles.

 

 

 

I was staggered to discover that the latest set of data I pulled of the VAG DPF app showed the last regen interval was some 375 miles!!!

 

I can’t explain how the cleaning of the throttle valve assy and the rotating of the exhaust gas nozzle has made such a difference. Yes it’s cleaner and very slightly less restricted. The last tank fill to fill also seems to show a slight mpg improvement. Again I wasn’t expecting that. I will continue to monitor and post any updates. The car is not doing a high mileage, maybe 6 to 8K a year and its now 6 years old and only done 50K.

 

Attached some data graphs to show the regen below...

 

 

 

 

 

 

 

 Excellent info, thanks

 

Tempted to have a peep in my TV now. I was under the impression the purpose of the TV on these engines is purely to reduce the flow of air when not needed, to prevent cooling of the DPF, to keep it as hot as possible (and maintain some passive regeneration effect).

 

Interesting to see from your first graph that it's always the calculated soot mass that rises highest; and that the measured soot mass sometimes goes negative. Mine does exactly the same and I always thought it looked "odd".

While the measured soot mass can decrease during certain driving conditions (generally starts to decrease when DPF temps get to around 300ºC), the calculated soot mass rarely drops - it only ever does so if I get the DPF really hot - IE same temps as during an active regen.

 

[burntcrisps2]

16 hours ago, voxmagna said:

I've also had a water softener for years. Bet you haven't rejuvenated the resin bed after several years use and contamination? I don't throw it away and replace now. Next year I think I'll just disconnect the exhaust gas return pipe, pull out the 'diverter' insert on the T.V and put my snake cam in for a look. With the ignition 'on' the T.V flap should be open, I've not been around the EGR cooler rear end at the back, which is so hard to see. Do you know where the hole with the pipe flange going into the cyl. head comes out? That also seems a good candidate for a snake cam look see.

Afraid you loose the bet on the resin beads replacement. Been there and done that. Some 40 years now and only on second water softener. The first one eventually wore out the mechanics, due I guess to very fine particulates.

I have not got a snake cam yet, but did look at them pre-Xmas so may get one soon.

TV flap is definitely open with ignition just turned on as tried this. Wondered if the flap moved at all when throttle pressed, but it doesn’t move at all. Suspect engine has to be running to see any movement. I might try next time I remove. It would be good to find the full info on what this TV actually does, when and why in the closed loop system. I must fully close when the engine is turned off as a way to kill the airflow and stall the engine. Not sure I understand which pipe flange you mean. If it’s the shiny metal one feeding into the inlet manifold, the other end of that goes into the engine block, which I assume goes to the egr side of things. Will have a look and see if I can see any drawings which show this.

 

[voxmagna]

Quote

Afraid you loose the bet on the resin beads replacement

 

My softener takes 2.5 bags of resin beads. I didn't just buy expensive bags of Purolite resin and replace it. I studied the chemistry, bought the correct acids and neutralizing alkali, all made up to the correct solution concentration, then used my own de-ionized water for flushing. Have you done that?

 

Since my TV intervention I now have a cleaned up working spare TV. The spare can be plugged in outboard and I thought it was useful as a quick check to see if other fault codes cleared or stayed put. On a standard engine there are only two variables for the TV - the TV itself and the accelerator - I have a spare for both.

 

On my 'fixed' EA189 if I turn on the key and waggle the accelerator pedal, the normally open flap starts closing, the flap motor is pretty responsive . But I can't remember now if that was with the engine idling or not because my spare TV was plugged in outboard? If the flap is stopped from closing in an ECU re-map, the air intake will not be starved and the dpf will not reach the high temperatures if it is actually starting regen. cycles.  It has at least 3 functions I know of: It adjusts (starves) airflow variably tending towards close when the accelerator pedal is pressed at low speed idle (NOX reduction?). It closes and stops diesel engine run on after key off.  It regulates (starves) the engine of air during dpf regeneration.

 

This sounds like a conflict when you would expect a performance drop? But VAG say they 'compensate' for reduced air intake so drivers do not notice any performance drop, which I assume means increasing the fuel injected on the power stroke. You probably already know they get the dpf up to those high temperatures >700C by firing the fuel injectors a second time, just before the exhaust stroke. That extra fuel added to the combustion exhaust gases is what burns in the dpf (and reduces mpg). The TV flap and EGR work together to hold the high dpf temperature constant during regen. I have to repeat a regen. test drive on the fixed CFHC Yeti, but when I did it on an older VAG car the temperature held constant at 708C for 15-20 minutes.

 

That's why re-mapping and not knowing what goes on concerns me? No regens at all will eventually block the dpf if it is still there. Uncontrolled dpf temperatures during regen are a potential fire hazard and could shorten the life of exhaust gas sensors. I don't think there is much safety margin above 700C for their sensors. Most generic sensors of this type are spec'd to 850C maximum.

 

Quote

If it’s the shiny metal one feeding into the inlet manifold, the other end of that goes into the engine block, which I assume goes to the egr side of things. Will have a look and see if I can see any drawings which show this.

 

That's the one. I am interested in the route that hole takes through the head (to the EGR valve?) and how far along I could get a snake cam?  With a magnet pickup it is fairly easy to remove that pipe and look both ways. Anybody with a CFHC engine head off on the bench would know?

 

The TV valve body has very simple electronics compared to other VAG parts. The valve body only has 2 electronic parts, a 5 volt d.c motor which can be reversed by changing polarity, a fixed permanent magnet in the nylon gear and a Hall effect sensor underneath which feeds back the flap position. The electronic control module monitors the flap position at key on when it expects it to be fully open. It will also know if the motor is bad or has intermittent brushes. If it gets partially stuck as in my case, you got an error code. It is easy to see why there are cheap aftermarket no-name TV valve clones, because most of the manufacturing work is mechanical to produce the valve body.

.

Edited 8 January, 2018 by voxmagna

[burntcrisps2]

3 hours ago, muddyboots said:

 Excellent info, thanks

 

Tempted to have a peep in my TV now. I was under the impression the purpose of the TV on these engines is purely to reduce the flow of air when not needed, to prevent cooling of the DPF, to keep it as hot as possible (and maintain some passive regeneration effect).

 

Interesting to see from your first graph that it's always the calculated soot mass that rises highest; and that the measured soot mass sometimes goes negative. Mine does exactly the same and I always thought it looked "odd".

While the measured soot mass can decrease during certain driving conditions (generally starts to decrease when DPF temps get to around 300ºC), the calculated soot mass rarely drops - it only ever does so if I get the DPF really hot - IE same temps as during an active regen.

 

It’s interesting to note the last regen shows the soot mass measured as only being half what it was in previous regens. Not sure why that should be either. Will need some more data logged to see if that is step change also. Looks like we will be doing some more motorway and longer runs in next few weeks, so should have some data to post later this month.

[voxmagna]

I don't think the soot and ash mass figures are precise science? They are not actually weighed but derived from VAG 'algorithms' based on dpf pressure drop, mass airflow, mileage and may be other things? What you see are numbers calculated by a computer and not measured quantities. However, it is those calculated figures that 'trip' the V.W threshold settings and either send you off to the garage for a manual regen. or if it goes to the second higher threshold, a new dpf! It is converted ash from regens retained in the dpf that determines normal end of life. But if soot levels are also allowed to rise to their preset threshold limit, V.W will not allow a manual forced regen. via diagnostics because of a fire risk. Monitoring soot, ash and pressure drops is important to avoid dash warnings and a choked dpf, particularly if you are running with a remap (or ECU fix).

 

I got a bit curious about this because I wondered what might happen if you used vcds to reset the system for a new dpf starting with zero soot and ash loads? Then I remembered they measure pressure drop across the dpf. Their algorithm considering all things, will prioritize and I suspect pressure drop being a real value will be top of the list. That being the case, fault management would still blow a raspberry for a dpf 'full' or needing active regen. intervention.

 

I use vcds quite a lot and it frequently appears to give bogus figures, the wrong unit labels or decimal points in the wrong place. Most diagnostics readers only read raw data which I am told is what vcds does, leaving you to guess what they mean. I would just look at the numbers and ignore the sign if the numeric value still makes sense. It's a different problem with pressure sensor measurements though because they are adapted (calibrated) when fitted to give positive pressure values referenced to sea level. Without the engine running and zero sensor pressures I have seen small negative pressure offset values. If these values are used in calculations the final result will be numerically negative and that's the raw data you get.  Dealer VAG diagnostics equipment is likely to interpret signed raw data and only show positive values, or put up a warning about a negative offset value coming from a sensor somewhere.

[burntcrisps2]

On 08/01/2018 at 11:39, voxmagna said:

 

My softener takes 2.5 bags of resin beads. I didn't just buy expensive bags of Purolite resin and replace it. I studied the chemistry, bought the correct acids and neutralizing alkali, all made up to the correct solution concentration, then used my own de-ionized water for flushing. Have you done that?

 

Since my TV intervention I now have a cleaned up working spare TV. The spare can be plugged in outboard and I thought it was useful as a quick check to see if other fault codes cleared or stayed put. On a standard engine there are only two variables for the TV - the TV itself and the accelerator - I have a spare for both.

 

On my 'fixed' EA189 if I turn on the key and waggle the accelerator pedal, the normally open flap starts closing, the flap motor is pretty responsive . But I can't remember now if that was with the engine idling or not because my spare TV was plugged in outboard? If the flap is stopped from closing in an ECU re-map, the air intake will not be starved and the dpf will not reach the high temperatures if it is actually starting regen. cycles.  It has at least 3 functions I know of: It adjusts (starves) airflow variably tending towards close when the accelerator pedal is pressed at low speed idle (NOX reduction?). It closes and stops diesel engine run on after key off.  It regulates (starves) the engine of air during dpf regeneration.

 

This sounds like a conflict when you would expect a performance drop? But VAG say they 'compensate' for reduced air intake so drivers do not notice any performance drop, which I assume means increasing the fuel injected on the power stroke. You probably already know they get the dpf up to those high temperatures >700C by firing the fuel injectors a second time, just before the exhaust stroke. That extra fuel added to the combustion exhaust gases is what burns in the dpf (and reduces mpg). The TV flap and EGR work together to hold the high dpf temperature constant during regen. I have to repeat a regen. test drive on the fixed CFHC Yeti, but when I did it on an older VAG car the temperature held constant at 708C for 15-20 minutes.

 

That's why re-mapping and not knowing what goes on concerns me? No regens at all will eventually block the dpf if it is still there. Uncontrolled dpf temperatures during regen are a potential fire hazard and could shorten the life of exhaust gas sensors. I don't think there is much safety margin above 700C for their sensors. Most generic sensors of this type are spec'd to 850C maximum.

 

 

That's the one. I am interested in the route that hole takes through the head (to the EGR valve?) and how far along I could get a snake cam?  With a magnet pickup it is fairly easy to remove that pipe and look both ways. Anybody with a CFHC engine head off on the bench would know?

 

The TV valve body has very simple electronics compared to other VAG parts. The valve body only has 2 electronic parts, a 5 volt d.c motor which can be reversed by changing polarity, a fixed permanent magnet in the nylon gear and a Hall effect sensor underneath which feeds back the flap position. The electronic control module monitors the flap position at key on when it expects it to be fully open. It will also know if the motor is bad or has intermittent brushes. If it gets partially stuck as in my case, you got an error code. It is easy to see why there are cheap aftermarket no-name TV valve clones, because most of the manufacturing work is mechanical to produce the valve body.

.

Looking at what diagrams and schematics are available in elsawin it looks like it just goes straight through the head/block and then on the rear of the engine there is another similar looking pipe, but with 2x 90degree bends that take it into the outlet of the egr cooler. Attached some pdfs that sort of show this.

This is a reasonable image of the egr cooler...

and the pipe connects the left hand port as you look at pic. Not sure looking back down that pipe is going to show you an awful lot, but no harm in looking.

I think the gunk build up is usually at and aroung the point of in and egr mixing.

 

Oh and I also found the method of diconnecting the air filter inlet pipework U shaped bit.

Info was buried in the radiartor removal... of all places.

 

 

Air intake pipework removal (part of remove radiator).pdf

Checking change-over flap for radiator for exhaust gas recirculation.pdf

Exhaust gas recirculation system overview.pdf

Exhaust gas recirculation with radiator - Summary of components.pdf

Removing and installing radiator for exhaust gas recirculation with exhaust gas recirculation valve -N18-.pdf

[voxmagna]

Thanks that's really helpful.  I'll do most jobs on Yeti, but had to get the EGR cooler replaced in the middle of Winter. The shop instructions to get to it on the 4X4 scared the s*it out of me with just ramps and working outside. As it's my partners car, she paid for the garage to do it. That's why I've never been around the back, but I suspect like the TV, the EGR might be repairable. Funny thing is whenever I can get the Stealer to talk to me, they always tell me there are updated parts. That was before the EA189 fix, so I don't know what porkies they now tell diesel customers with fault lights on? Have you ever dropped a sub-frame and lowered these engines? i know there's a lot to disconnect, but I was wondering with an engine crane and ramps, if that's option to work on the 4X4 rear? In the factory I think they raise the engine inside the body or lift the body over the engine.

 

From your photo it looks like the 'hole in the head' is just that - to pass exhaust gases from the rear to the front. As you say, it doesn't look like a snake cam would get inside the EGR assembly and make any sense of what it saw. As I mentioned, these snake cams often give distorted images and they really only help if you have seen what the inside of parts look like first. Therefore I would be o.k on the TV. although seeing black might be a problem with their puny led illumination.

 

When you look at that EGR cooler it seems like a marvel of engineering, but what comes out after mileage is something grubby and gummed up with soot? I could see soot on the head link hole and assumed it must be like that all the way back since they've cooled the exhaust gases to pull out more NOx.. Good job it's cooled, because the plastic inlet manifold and TV flap might not take the heat?

.

Edited 9 January, 2018 by voxmagna

[burntcrisps2]

On 09/01/2018 at 22:38, voxmagna said:

Thanks that's really helpful.  I'll do most jobs on Yeti, but had to get the EGR cooler replaced in the middle of Winter. The shop instructions to get to it on the 4X4 scared the s*it out of me with just ramps and working outside. As it's my partners car, she paid for the garage to do it. That's why I've never been around the back, but I suspect like the TV, the EGR might be repairable. Funny thing is whenever I can get the Stealer to talk to me, they always tell me there are updated parts. That was before the EA189 fix, so I don't know what porkies they now tell diesel customers with fault lights on? Have you ever dropped a sub-frame and lowered these engines? i know there's a lot to disconnect, but I was wondering with an engine crane and ramps, if that's option to work on the 4X4 rear? In the factory I think they raise the engine inside the body or lift the body over the engine.

 

From your photo it looks like the 'hole in the head' is just that - to pass exhaust gases from the rear to the front. As you say, it doesn't look like a snake cam would get inside the EGR assembly and make any sense of what it saw. As I mentioned, these snake cams often give distorted images and they really only help if you have seen what the inside of parts look like first. Therefore I would be o.k on the TV. although seeing black might be a problem with their puny led illumination.

 

When you look at that EGR cooler it seems like a marvel of engineering, but what comes out after mileage is something grubby and gummed up with soot? I could see soot on the head link hole and assumed it must be like that all the way back since they've cooled the exhaust gases to pull out more NOx.. Good job it's cooled, because the plastic inlet manifold and TV flap might not take the heat?

.

Never had to take the engine out of the Yeti and as you the factory instructions like dire, so not planning on doing myself. But as is the way with a lot of factory instructions, if theres a will tehres a way to do some other way.

Looks like it needs to come up and out, have attached the pdfs here for others should they need to review also.

 

The EGR cooler looks similar in overall construction to an oil cooler. My son had oil cooler fail on his Mondeo Estate and oil gets into the water system. Its a pain to replace and even more of a pain to clean the waterways afterwards. He got a local garage to do, but took a couple of water clean cycles to get it sorted over a number of weeks. Since they do fail, I decided to do the one on our Ford Focus and that is nicely hidden round the back of the engine. Its a pain just to change the oil filter as its horizontal and no matter how careful, always dribbles oil onto the inner CV rubber of the offside driveshaft. New oil cooler came with a new oil filter pre-fitted, but you need it off to wiggle the assembly into place. Just unscrew the new filter turned into actually having to desctroy it to get it off. No idea how they had managed to attach so it couldnt be removed without a vice. Just as well I had to remove as it would never have come off if it could have been fitted with it on.

Removing engine - Installing the engine.pdf

Removing engine - Securing the engine to the assembly stand.pdf

Removing engine - special tools and equipment reqd..pdf

Removing engine - Unit mounting - summary of components.pdf

[voxmagna]

Thanks for the pdf links, I'll study them. As you say, there are often shortcuts. I know the Stealer replaced my Yeti 4X4 EGR cooler assembly in a day, muttered something about a quicker way than the shop procedure. They wouldn't tell me what that was but if you've got a 4 post ramp it's a good start. Some of these shop procedures look scary when written down, but if you've done car work for years, many things are just 'look and take off'.  However, I accept that taking more off may seem a long way around at the time, but mental stress and torture trying to work around something can often take longer. Looks like Yeti engine comes out from the bottom. I don't know if it would work here, but I read somebody with a VAG slackened off engine mountings and attachments and was able to rotate the engine forwards sufficiently to get more room at the back around the EGR and dpf?

.

Edited 17 January, 2018 by voxmagna

[burntcrisps2]

I am continuing logging regen info. until we get cgon unit fitted. Seems the next regen was much shorter in miles, but that was actually due to being in an hour long traffic jam, so to be expected. The regen distance is still higher, but only ~240miles rather than the first one at ~375miles after throttle valve clean. Not sure why it should have been so high after clean, but still seems better than before.

 

[voxmagna]

I've been thinking some more about what 'dpf regeneration' actually means. I remember reading in V.W notes that driving high speeds for longer distances when high exhaust gas temperatures (effectively burning soot in the dpf) changes the pattern of when an automatic regen is carried out. I managed to build a simple led bargraph module to monitor the bank 1 dpf temperature sensor in real time. I tried it out on a V.W TDi with a stage 1 tune and no ECU fix.

 

For normal use of the gas pedal, my EG temperature would rise to around 500C when I thought those temperatures could only be reached with forced regeneration? But under hard acceleration EG temperatures shoot up to over 700C! It was quite revealing to watch how the EG temperature would change rapidly according to how the car was driven. It also showed differences driving at the same road speed in a higher or lower gear, which might correlate to mpg. Temperature figures reported by the ECU  from EG sensors via diagnostics are processed and averaged, what you see isn't exactly what happens in real time.

 

The EG sensors are measuring the gas temperature which changes rapidly and not the actual dpf filter temperature which needs time to stabilize. They cannot measure the dpf core temperature directly, because there's no contact type temperature sensor. They must use an algorithm to monitor the EG temperature over units of time and build in a factor something like: The dpf core temperature is x degrees when the EG temperature x is maintained for y minutes? That might explain why cruising at high speeds should keep the EG temperature high and regular mileage based active regens shouldn't be needed? When regen. is needed, the system holds the EG temperature at around 700C and they allow 15-20 minutes to complete, because I think that is the lag time they allow to ensure the dpf core gets up to temperature. If this is true, then distances measured between regens might vary according to the distance, time and speeds traveled.  For shortish commutes I would expect regen mileage intervals to be fairly predictable and more frequent.

 

My V.W could be running hotter than the Yeti and when I've finished working on the electronic monitor, I'll switch it over to the Yeti with the ECU fix and see how that compares. I'm curious about your cgon unit because if it works without frequent regenerations requested by the ECU, what stops the ECU from still trying to do regens? The ECU knows nothing about hydrogen, it will do what it does based on inputs from the vehicle sensors and the ECU algorithms?  It might raise the EG temperature like a stage tune, but then wouldn't that be a preferred option? I'm just a bit sceptical of their claims and its effectiveness.

[burntcrisps2]

If anybody is reading this thread for the first time, I can report that the fault code has not returned since doing the cleaning and the car has been running without any issue for about 8months now.

I am still logging regen cycles and its settled down to the roughly 200miles between, but depends on driving/journeys as expected.